1. Field of the Invention
This application relates to a photo alignment material and a method of manufacturing display substrate using the same. More particularly, this application relate to a photo alignment material that may be used for manufacturing an alignment layer of a liquid crystal display device and a method of manufacturing display substrate using the same.
2. Description of the Related Art
Generally, liquid crystal display (“LCD”) panels include in their construction an array substrate having switching devices for driving pixels, an opposing substrate facing the array substrate and a liquid crystal layer interposed between the array substrate and the opposing substrate. A voltage applied to the liquid crystal layer of the LCD panel controls the transmittance of light through the LCD panel and thence through selected pixels, to allow the display of an image.
A liquid crystal material interposed between the substrates forms the liquid crystal layer. In addition, an alignment layer is formed on each of the opposing inner surface of the substrates so as to make contact with and align the liquid crystal material in a desired direction. Alignment layers may be formed by, for example, coating a solution including a polyimide on a surface of the substrate with a printing roller of an alignment layer printing device, and then rubbing to form the alignment layer.
However, the rubbing fabric used in rubbing processes can cause a buildup in static electricity, which can thereby damage patterns on the substrate. Furthermore, the substrate may be contaminated by impurities on or in the rubbing fabric, and visual defects such as blurs may appear on the substrate so that the overall display quality deteriorates. To address the above-mentioned problems, photo alignment methods have been investigated. In photo alignment methods, a photo alignment material is first coated on a surface of a substrate, and then exposed to light. The photo alignment material is thereby photo-decomposed, photo-isomerized or photo-polymerized to form an alignment layer having a predetermined orientation.
Meanwhile, voltage is applied to a pixel electrode and a common electrode of a LCD panel, the alignment layer manufactured by the photo alignment method may be damaged by electric stress. Thus, orientation of the alignment layer may not be maintained uniformly, and the tilted angle of a liquid crystal molecule on the alignment layer may change. Accordingly, a difference in brightness between black and white may be caused in the gray scale level. The brightness difference may be observable as a residual image, thereby deteriorating the display quality.